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[formulas] Handle geodesics lying on equator in Thomas direct.

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Adam Wulkiewicz
2016-07-30 04:20:13 +02:00
parent 2a426d2211
commit 39ea7f4bc8
1 changed files with 11 additions and 1 deletions
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12
include/boost/geometry/formulas/thomas_direct.hpp
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@@ -106,7 +106,17 @@ public:
CT const D = (c1 - C2) * (c1 - C2 - C1 * M);
CT const P = C2 * (c1 + C1 * M / c2) / D;
CT const cos_sigma1 = sin_theta1 / sin_theta0;
// special case for equator:
// sin_theta0 = 0 <=> lat1 = 0 ^ |azimuth12| = pi/2
// NOTE: in this case it doesn't matter what's the value of cos_sigma1 because
// theta1=0, theta0=0, M=1|-1, C2=0 so X=0 and Y=0 so d_sigma=d
// cos_a12=0 so N=0, therefore
// lat2=0, azi21=pi/2|-pi/2
// d_eta = atan2(sin_d_sigma, cos_d_sigma)
// H = C1 * d_sigma
CT const cos_sigma1 = math::equals(sin_theta0, c0)
? c1
: sin_theta1 / sin_theta0;
CT const sigma1 = acos(cos_sigma1);
CT const d = distance / (a * D);
CT const u = 2 * (sigma1 - d);